Field
The present disclosure relates generally to data center path switches typically used in data centers of enterprise networks and service provider networks, and more particularly to high density data center path switches having the capability of switching entire data paths with low latency path interconnections between input ports and the output ports.
Description of the Related Art
Telecommunication switching has a long history, evolving from manual switching to early automatic electro-mechanical switching systems, such as step-by-step switching systems and crossbar switching systems, to more recent electronic and optical switching systems.
Digital and optical switching systems allowed for substantial growth in the size of electronic switching systems to meet the needs of ever expanding communication networks. The progression to the more common digital and optical switching systems was spurred on a belief that newer semiconductor (e.g., VLSI) and optical devices met the need for high speed data transmissions.
With the evolution of telecommunication switching has been the evolution of computers and the information age. In order to manage the increase in data transmissions between computers, data centers came to be. Data centers have their roots in the huge computer rooms built during the early ages of the computing industry. Early computer systems were complex to operate and maintain, and required a special environment in which to operate. During the boom of the microcomputer industry in the 1980s, computers started to be deployed everywhere and systems, such as dedicated computers or servers, were developed to meet the demands created by the need to have the increasing number of computers communicate. During the latter part of the 20th century and early part of the 21st century, data centers grew significantly to meet the needs of the Internet Age. To maintain business continuity and grow revenue, companies needed fast Internet connectivity and nonstop operations to establish a presence on the Internet.
Today, data centers are built within the enterprise network, a service provider network, or a shared, colocation facility where the networks of many disparate owners reside. With the significant increase in business and individual use of the Internet, and the significant need for bandwidth to transmit high volumes of data, especially video and graphics, data centers are again under pressure to evolve to handle the boom in growth. However, data centers are typically very expensive to build, operate and maintain, and data center operators are searching for ways to reduce costs while increasing data processing and transmission capabilities, while meeting all reliability requirements.
To meet the ever increasing demands, network architectures have evolved over the years to address these pressures, with old methodologies and technologies giving way to newer and supposedly faster methodologies and technologies.
In order to meet the increased demands, data center network architectures have changed. Sometimes the changes to the network architecture require significant rerouting of network connections, and sometimes the network architecture needs to be dynamic, changing frequently. And, all this has to be achieved at today's fast rates with little or no failures or delays in the transmission of data.
To address such pressures data center network switches have evolved with the capability of switching data traffic on a packet-by-packet basis, which is known as packet switching. While packet switching can change the physical route of individual packets through the network, there are some network applications where the requirement is to switch all the data traffic from one physical route to a second physical route through the network, which is known as port switching, or path switching.
As seen in FIG. 1, current data center data center network switch architectures have a number of ports 108 interconnected by a switching core. The data center network switch 10 in FIG. 1 has a number of ports 108, switch logic 106, and a Central Processing Unit (CPU) 102. The data center network switch 10 may also have a management interface unit 104 that enables the data center network switch 10 to communicate with a management control unit 100 that configures the settings within data center network switch 10.
Each port 108 connects to switch logic 106 via data path 118. In operation, switch logic 106 receives a data stream from a particular port 108 and transfers or switches the data stream to an outgoing port 108 as defined by configuration settings from management control unit 100.
FIG. 2 shows more details of the architecture of the switch logic 106. Port 108, also called a transceiver, has a receiver which receives a data stream from a remote end via external medium 126, and a transmitter which transmits a data stream to the remote end via external medium 126. Path 118, between port 108 and switch logic 106, is shown here separated into two paths: path 114 is the data flow direction from port 108 to switch logic 106 which is referred to here as the receive direction, while path 112 is the data flow direction from switch logic 106 to port 108, which is referred to here as the transmit direction.
The data center network switch 10 receives a Physical Layer data stream on an input port 108A, extracts packets (e.g., the data and header information) from the data stream via switch logic 106, and then transmits the packets (e.g., the data and header information) out a Physical Layer data stream on output port 108B. More specifically, in the data center network switch configuration of FIG. 2, port 108A receives a Physical Layer data stream (or signal) from the external medium 126A, which may be a wireless, Cat 6, Cat 6a, optical fiber, or other physical connection, and converts the data stream (or signal) from the Physical Layer data stream (or signal) form into an electrical data signal that can be used within the switch logic, separates the serial data and recovered timing information from the Physical Layer data stream (or signal), and passes the serial data stream, via connection 114A, into a Serial/Deserializer 120 (here SerDes 120A). The SerDes 120A converts the serial data stream into a parallel interface format for Media Access Control (MAC) sub-layer 122A. The MAC sub-layer 122A is an interface between a network's Data Link Layer's Logical Link Control (LLC) sub-layer and its Physical Layer, and provides the network's Data Link Layer functions, including frame delimiting and identification, error checking, MAC addressing, and other functions. Packets are parsed by the MAC layer 122A, where header fields are extracted and passed via interface bus 110 to CPU 102, which interprets the header information.
The data center network switch management control unit 100 communicates information, such as configuration information, alarm information, status information, to the management interface unit 104, via control path 116. Routing tables 128 contain information to direct incoming packets on a particular port 108 to outgoing packets on a particular port 108. The Routing tables 128 may be determined by known discovery protocol software within data center network switch 10, or CPU 102 may receive configuration information from the management control unit 100 to set up a particular routing table configuration. CPU 102 looks up the output destination route for a packet, and modifies the outgoing packet header, if necessary.
Switch fabric 124 then transfers the packet to an outgoing queue in outgoing MAC layer 122B. Outgoing MAC layer 122B formats the outgoing packet for transmission, and performs other Data Link Layer functions, such as generating a frame check sequence for outgoing packets. The completed packet is then fed to outgoing SerDes 120B, which converts the parallel data stream into a serial data stream. The serial data stream is then fed to the outgoing port 108B, which converts the data stream into a physical layer signal, adds physical layer timing, and transmits the physical layer signal out port 108B to external medium 126B.
Within current data center network switches 10, the number of steps to transfer an incoming physical layer signal from an incoming port 108 to an outgoing port 108 adds transmission delays and necessitates modifications to the outgoing packet. The current state of packet switches has latency issues of about and in excess of 500 nsec per packet, which is insufficient for today's data centers.
Further, a single data center network switch core can support only a relatively small number of ports. For a very large number of ports, data center network switch cores have to be configured in hierarchical or mesh configurations, which adds complexity to the network, decreases reliability, and further increases latency.
Turning to path switching, in today's data centers, network applications may employ; 1) an electrical-electrical-electrical path switch, 2) an electrical-optical-electrical path switch, 3) an optical-electrical-optical path switch, and/or 4) an optical-optical-optical path switch.
Various switching techniques have been used to implement such path switching methodologies. Examples include crosspoint switching, space switching, time slot switching, and wavelength switching to interconnect paths from an incoming port to outgoing port. However, today's demand for higher port counts in data center path switches restricts the above path switching techniques that may be employed to achieve high density, high speed path switching. Factors associated with such path switching techniques, such as high cost, low manufacturing yield, low reliability, high data latency, signal loss, power consumption, heat dissipation, and real estate, have heretofore prevented the expansion of path switching in today's high speed, high density data center data center path switches.
Currently available optical crosspoint switching technologies include electronic crosspoint switches, waveguides, beam steering, Micro-Electro-Mechanical Systems (MEMS), tunable filters, liquid crystal switching, and thermo-optical polymers solutions.
However, MEMS for example, has low reliability due to moving parts (e.g., mirrors), and requires corrective circuitry to ensure accurate beam alignment to correct for mirror misalignment. Another problem with MEMS is that as the number of ports being switched increases, the number of mirrors must significantly increase, further increasing the low reliability, mirror misalignment and path set up latency concerns. Increasing the number of mirrors also leads to more distance between the ports and the mirrors, which creates an issue known as beam divergence, where each individual beam widens as it passes from mirror to mirror resulting in signal loss along the path.
Physical sizes of MEMS hardware is also a problem and there are cost issue with current MEMS applications. For example, to create 320×320 port solutions in a MEMS application would require a physical size of 7 data center Rack Units (RU) in a data center cabinet or rack.
Beam steering has similar issues where as the number of ports to interconnect rises, the angular range increases and alignment and distortion effects exceed the capabilities of transmitting reliable signals.
With waveguide crosspoint switching, methods of path interconnections using ink-jet or thermo capillary techniques to pass or reflect an optical signal along the waveguide. However, using ink-jet or thermo capillary techniques to pass or reflect an optical signal along a waveguide typically generates significant heat, which creates heat dissipation and reliability issues.
Further, the different optical crosspoint switching techniques noted above are not capable of scaling in size to support large production applications required in today's data center networks. With most of these crosspoint path switching techniques, complexity and costs rise exponentially as the number of ports increases making it very expensive to meet the demands on today's data centers.